1. DS11 T Transfer function, integral field and coil length
Susana Izquierdo Bermudez, Lucio Fiscarelli
Acknowledgments: Frederic Savary, Herve Prin, Luca Bottura
31sOctober 2017
109th HiLumi WP2 Meeting

2. Requirements and design evolution
MBHDP102/ Prototype/ Series
MBHDP101
Requirement:
119.2 Tm at kA
Main design evolution features from the first to the second short model (and prototype):
Outer yoke radius 275 mm  270 mm (to be compatible with LHC-MB tooling)
Iron laminations at the magnet extremities replaced by non-magnetic laminations (to decrease the peak field in the coil ends)
Due to time constrains and additional uncertainty on the final coil length (mainly due to the lack of experience in terms of dimensional changes during heat treatment in 5.5 m length Nb3Sn coils), the coil length of the prototype coils was not modified to account for the design evolution.
Aim of today: summarize the available data from the short model program (and prototype collared coils assemblies) and propose adjustments for the series coils.

3. Collared coil magnetic measurements (RT)
Transfer function in the straight section, integral field and magnetic length is within 10 units the expected values
Difference among apertures in terms of integral field:
Around 25 (σ) units in the short models (6 apertures measured)
Around 10 (σ) units in the prototype (3 apertures measured)
Collared Coil
Room temperature measurements (± 20 A)
Short models
Prototype
TF (T/kA) Central Segment
Integral (Tm/kA)
Magnetic length (mm)
Average all single apertures
0.7969
1.3460
1689
0.7940
4.2221
5317.8
STD (units) 7 23 21 2 6
ROXIE 3D
0.7972
1.3473
1690
0.7947
4.2272
5319
diff to ROXIE 2D (units) 28
n.a
-10
diff to ROXIE 3D (units) -4 -7
-12 -2

4. Cold mass magnetic measurements (RT)
DP102 and Prototype
Field in the magnet centre is within 10 units the expected value for the double aperture magnets.
Integral field is 24 units larger than measured in average, with difference in between the two apertures up to 36 units.
In the single aperture models, the difference in between magnets was up to 60 units.
DP101
Cold Mass
Room temperature measurements (± 20 A)
(double aperture)
TF (T/kA) Central Segment
Integral (Tm/kA)
Magnetic length (mm)
Magnet
DP101
DP102
Average two apertures
0.9903
0.9910
1.6772
1.6627
1694
1678
STD (units) 1 5 18 6 17
ROXIE 3D
0.9912
0.9909
1.6732
1.6587
1688
1674
diff to ROXIE 2D (units)
-20
-12
n.a
diff to ROXIE 3D (units) -9 24 33 23

5. Magnetic measurement operation conditions
Iron saturation effects are well captured by ROXIE when considering the 3D model.
The measured field in the straight part is within 10 units the expected value for all current levels.
Since measurements in the short models are performed using a rotating shaft at cold, there is not an accurate evaluation of the integral field and magnetic length available.
Susana Izquierdo Bermudez

6. From short model experience to prototype and series magnets
Expected field in the prototype magnet
Cold mass, RT - 20 A
1.9 K, kA
TF (T/kA)
(±10 units)
(±10 units)
Integral (Tm/kA)
(+20, -10 units)
(+20, -10 units)
REQUIREMENT:
Lm (mm)
5280 (+20, -10 units)
5264 (+20, -10 units)
Possible action to adjust integral field in the series magnets:
Option 1: Physical coil length is modified in order to reach the target integral field in the series magnet
Coil has to be mm longer than in the prototype
Option 2: The difference on the integral field with respect to the target is compensated using the trim circuit
This will mean that at nominal magnet current, the trim should operate at A (instead of ~ 0 A)

7. Proposed solution
Increase the coil physical length by 40 mm in the straight section. This action can be done with minor impact in the cold mass assembly and coil production process.
After the full magnetic characterization of the prototype magnet, a more accurate evaluation of the expected field for the series magnets can be done. Deviations from nominal case can still be corrected by:
Increasing or reducing the number of non-magnetic laminations in the magnet extremities.
Maximum increase of the magnetic length is 14 mm, and increases the peak field in the coil ends by 0.2 T.
Modifying the trim circuit current profile.
10 mm deviation on the magnetic length corresponds to ~ 20 A shift in the trim circuit current at nominal current.

8. Additional slides

9. Feedback from short models program
MBHSP101*
MBHSP102
MBHSP103
MBHSP104/4b
MBHSP105/5b
Coil 106
(RRP 108/127)
Coil 106
(RRP 108/127)
Coil 109
(RRP 132/169)
Coil 112
(RRP 132/169)
Coil 114
(RRP 150/169)
Coil 107 (limiting coil)
(RRP 108/127)
Coil 108
(RRP 132/169)
Coil 111
(RRP 132/169)
Coil 113 (limiting coil)
 109 in SP104b
(RRP 132/169)
Coil 115
(RRP 150/169)
Assembled in MBHDP101
Assembled in MBHDP102
MBHSP#
MBHDP101
MBHDP102
* Magnetic measurements performed with a different shaft, issues on the collared coil measurements, calibration questionable, so not accounted for this analysis

10. Trim current assuming the prototype is 43 mm shorter than nominal

11. Coil Manufacturing data – Prototype coils
Collared Coil
CR0002
CR4
CR5
Start fabrication
23/02/2016
17/06/2016
End fabrication
16/03/2017
24/04/2017
Cross section ID
1st Gen
Conductor and cable
Strand lay-out
RRP 132/169
&150/169
Cable ID
H15OC0194A
H15OC0196A
Azimuthal coil size dev.(µm) 
Min
-58
-125
Max
165
228
25 % 30
-43
75 % 75 34
Median 54
-10
Average 52
Coil length (mm)
 LHCMBH_C0005
Nominal post length
5113
Nominal coil length
5559
Post length for winding
5111.5
5113.1
Post length after curing
5106.4
5108.6
Post length after react.
5110
5112
Post length after impr.
5113.2
Coil length after impr.
5560.8
Collared Coil
CR003
CR6
CR7
Start fabrication
09/02/2016
12/04/2016
End fabrication
/2017
Cross section ID
1st Gen
Conductor and cable
Strand lay-out
RRP 108/127
Cable ID
H15OC0209A
H15OC0210A
Azimuthal coil size dev.(µm) 
Min
-0.474
-0.222
Max
-0.038
0.390
25 %
-0.164
-0.020
75 %
-0.001
0.180
Median
-0.076
0.052
Average
-0.079
0.076
Coil length (mm)
 LHCMBH_C0005
Nominal post length
5113
Nominal coil length
5559
Post length for winding
5108
5109
Post length after curing
5107
Post length after react.
5114
Post length after impr.
5116
5110
Coil length after impr.
5560
5562
Coil Manufacturing Data from MTF